The ability to connect Android 4.+ devices to Ubuntu using the USB Mass Storage interface has always been a pain. With Ubuntu 13.04 a new MTP back-end (gvfs-mtp) is going to be introduced, but I have had some issues with the 13.04 Beta so I found this backport PPA to Ubuntu 12.04 and 12.10
sudo add-apt-repository ppa:langdalepl/gvfs-mtp
sudo apt-get update
sudo apt-get install gvfs
sudo apt-get upgrade
Kudos to Phillip Langdale for the work and maintaining the PPA !